The present invention relates to a high-frequency power amplifier, and relates, more particularly, to a class C power amplifier that uses a transistor as an amplifying element.
Among various kinds of digital modulations that are used for mobile communications or the like, there is a constant amplitude modulation system. In this constant amplitude modulation system, it is possible to use a class C power amplification. As is known well, class C power amplification is a system that has highest power amplification efficiency.
In other words, in general, while class A power amplification efficiency and class B power amplification efficiency are 50% and 70% respectively, class C power amplification efficiency is almost 100%.
However, the above 100% is an ideal value, and an actual value is far from this value. Further, in a high-frequency band of a several 100 MHz or above, to which the present invention refers, this value is much lower, and is about 50%, in reality. Generally known catalogs of amplifiers also show such a low value.
The fact that this power amplification efficiency is as low as about 50% in the high-frequency class C power amplifier has been reported as attributable to internal constants of transistors that form main portions of this amplifier. However, there has been a problem that, because of such low efficiency, the power consumption and the thermal loss of the high-frequency class C power amplifier are large.
In the light of the above problems, a cause of the low power amplification efficiency will be analyzed in the present invention. Further, it is an object of the present invention to provide a high-frequency power amplifier that can increase a realistic value from the conventional value of about 50% to about 70%.
In order to achieve the above object of the present invention, a current absorbing unit which absorbs a higher-harmonic frequency current contained in a signal of a fundamental wave (a fundamental amplification frequency) at which an amplifying element operates, is connected to an input side of the amplifying element.